The present invention relates to a brazed-plate heat exchanger, whose passages contain at least one corrugated fin of the type comprising, in cross section, a repeated corrugated pattern which extends between two upper and lower extreme planes defined by the plates of the exchanger.
The invention is in particular applicable to gas—gas cryogenic exchangers for air distillation apparatuses, such as the main heat exchange line of these apparatuses, which cools the incoming air by indirect heat exchange with the cold products from the distillation column.
The corrugated fins in question are widely used in brazed-plate heat exchangers, which have the advantage of offering a large heat exchange surface area in a relatively small volume, and of being easy to manufacture. In these exchangers, the fluid flows may be cocurrent, countercurrent or crosscurrent flows.
FIG. 1 of the appended drawings shows, in perspective, with partial cutaways, an example of such a heat exchanger, of conventional structure, to which the invention is applicable. In particular, it may involve a cryogenic heat exchanger.
The heat exchanger 1 shown consists of a stack of parallel rectangular plates 2 which are all identical and which between them define a plurality of passages for fluids to be brought into indirect heat exchange relationships. In the example shown, these passages are, in succession and cyclically, passages 3 for a first fluid, 4 for a second fluid and 5 for a third fluid.
Each passage 3 to 5 is bordered by closure bars 6 which define the passage, leaving inlet/outlet windows 7 of the corresponding fluid free. Placed in each passage are spacer waves or corrugated fins 8 acting both as thermal fins, as spacers between the plates, especially during brazing and in order to avoid any deformation of the plates when using pressurized fluids, and for guiding the fluid flows.
The stack of plates, closure bars and spacer waves is generally made of aluminum or aluminum alloy and is assembled in a single operation by furnace brazing.
Fluid inlet/outlet boxes 9, of semicylindrical overall shape, are then welded to the exchanger body thus produced so as to sit over the rows of corresponding inlet/outlet windows, these boxes being connected to fluid feed and discharge pipes 10.
There are various types of spacer waves 8. Thus mention may be made of straight fins, with rectilinear, possibly perforated, generatrices, fins known as “herringbone” fins, with sinuous generatrices, louvered fins, the wave legs of which have rows of recesses, and partially offset or “serrated” fins.
In these various fins, the wave may have a square, rectangular, triangular, sinusoidal, etc., cross section.